This invention pertains to a polishing disk comprising an end-point detection port, a method for producing such a polishing disk, and a method of using such a polishing disk.
The trend in the semiconductor industry continues to concentrate on reducing the size of semiconductor features while improving the planarity of their surfaces. More specifically, it is desirable to achieve a surface of even topography by decreasing the number and size of surface imperfections. A smooth topography is desirable because it is difficult to lithographically image and pattern layers applied to rough surfaces. A conventional method of planarizing the surfaces of these devices is to polish them with a polishing system.
The conventional method of planarizing semiconductor devices involves polishing the surface of the semiconductor with a polishing composition and a polishing disk, such as is accomplished by chemical-mechanical polishing (CMP). In a typical CMP process, a wafer is pressed against a polishing disk or pad in the presence of a polishing composition (also referred to as a polishing slurry) under controlled chemical, pressure, velocity, and temperature conditions. The polishing composition generally contains small, abrasive particles that mechanically abrade the surface of the wafer in a mixture with chemicals that chemically react with (e.g., remove and/or oxidize) the surface of the wafer. The polishing disk generally is a planar pad made from a continuous phase matrix material such as polyurethane. Thus, when the polishing disk and the wafer move with respect to each other, material is removed from the surface of the wafer mechanically by the abrasive particles and chemically by other components in the polishing composition.
In polishing the surface of a substrate, it is often advantageous to monitor the polishing process in situ. One method of monitoring the polishing process in situ involves the use of a polishing disk having an aperture or window. The aperture or window provides a portal through which light can pass to allow the inspection of the substrate surface during the polishing process. Polishing disks having apertures and windows are known and have been used to polish substrates, such as semiconductor devices. For example, U.S. Pat. No. 5,605,760 (Roberts) describes a polishing pad having a transparent window formed from a solid, uniform polymer, which has no intrinsic ability to absorb or transport a polishing composition. U.S. Pat. No. 5,433,651 (Lustig et al.) discloses a polishing pad wherein a portion of the pad has been removed to provide an aperture through which light can pass. U.S. Pat. Nos. 5,893,796 and 5,964,643 (both by Birang et al.) disclose removing a portion of a polishing disk to provide an aperture and placing a transparent polyurethane or quartz plug in the aperture to provide a transparent window, or removing a portion of the backing of a polishing disk to provide a translucency in the disk. While these devices with apertures or windows are initially effective for end-point detection, the polishing composition potentially can pool at the aperture and/or degrade the surface of the transparent window. Both of these effects diminish the ability to monitor the polishing process.
Thus, there remains a need for improved polishing disks and associated methods. The invention provides such a polishing system and a method of preparing and using such a polishing disk. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
The invention provides a polishing disk comprising (a) a body comprising a front surface, a back surface, and a peripheral surface, (b) a polishing surface, (c) an end-point detection port extending through the body from the front surface to the back surface, and (d) a drainage channel in fluid communication with the end-point detection port. The presence of the drainage channel assists in preventing a build-up of the polishing composition in the end-point detection port that inhibits end-point detection of a polishing process. The invention further provides method of preparing such a polishing disk and a method of polishing a substrate with such a polishing disk.